Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 1 | .\" |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 2 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 3 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 4 | .\" All rights reserved |
| 5 | .\" |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 6 | .\" As far as I am concerned, the code I have written for this software |
| 7 | .\" can be used freely for any purpose. Any derived versions of this |
| 8 | .\" software must be clearly marked as such, and if the derived work is |
| 9 | .\" incompatible with the protocol description in the RFC file, it must be |
| 10 | .\" called by a name other than "ssh" or "Secure Shell". |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 11 | .\" |
Ben Lindstrom | 92a2e38 | 2001-03-05 06:59:27 +0000 | [diff] [blame] | 12 | .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved. |
| 13 | .\" Copyright (c) 1999 Aaron Campbell. All rights reserved. |
| 14 | .\" Copyright (c) 1999 Theo de Raadt. All rights reserved. |
Damien Miller | e4340be | 2000-09-16 13:29:08 +1100 | [diff] [blame] | 15 | .\" |
| 16 | .\" Redistribution and use in source and binary forms, with or without |
| 17 | .\" modification, are permitted provided that the following conditions |
| 18 | .\" are met: |
| 19 | .\" 1. Redistributions of source code must retain the above copyright |
| 20 | .\" notice, this list of conditions and the following disclaimer. |
| 21 | .\" 2. Redistributions in binary form must reproduce the above copyright |
| 22 | .\" notice, this list of conditions and the following disclaimer in the |
| 23 | .\" documentation and/or other materials provided with the distribution. |
| 24 | .\" |
| 25 | .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| 26 | .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| 27 | .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| 28 | .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| 29 | .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| 30 | .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 31 | .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 32 | .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 33 | .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| 34 | .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 35 | .\" |
jmc@openbsd.org | 483cc72 | 2019-11-30 07:07:59 +0000 | [diff] [blame] | 36 | .\" $OpenBSD: sshd.8,v 1.308 2019/11/30 07:07:59 jmc Exp $ |
| 37 | .Dd $Mdocdate: November 30 2019 $ |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 38 | .Dt SSHD 8 |
| 39 | .Os |
| 40 | .Sh NAME |
| 41 | .Nm sshd |
jmc@openbsd.org | 483cc72 | 2019-11-30 07:07:59 +0000 | [diff] [blame] | 42 | .Nd OpenSSH daemon |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 43 | .Sh SYNOPSIS |
| 44 | .Nm sshd |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 45 | .Bk -words |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 46 | .Op Fl 46DdeiqTt |
Darren Tucker | e7140f2 | 2008-06-10 23:01:51 +1000 | [diff] [blame] | 47 | .Op Fl C Ar connection_spec |
Damien Miller | 0a80ca1 | 2010-02-27 07:55:05 +1100 | [diff] [blame] | 48 | .Op Fl c Ar host_certificate_file |
Damien Miller | 03d4d7e | 2013-04-23 15:21:06 +1000 | [diff] [blame] | 49 | .Op Fl E Ar log_file |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 50 | .Op Fl f Ar config_file |
| 51 | .Op Fl g Ar login_grace_time |
| 52 | .Op Fl h Ar host_key_file |
Ben Lindstrom | ade03f6 | 2001-12-06 18:22:17 +0000 | [diff] [blame] | 53 | .Op Fl o Ar option |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 54 | .Op Fl p Ar port |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 55 | .Op Fl u Ar len |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 56 | .Ek |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 57 | .Sh DESCRIPTION |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 58 | .Nm |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 59 | (OpenSSH Daemon) is the daemon program for |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 60 | .Xr ssh 1 . |
Damien Miller | 69cb24b | 2014-04-20 13:29:06 +1000 | [diff] [blame] | 61 | Together these programs replace rlogin and rsh, |
Darren Tucker | 04354b9 | 2007-03-21 20:46:54 +1100 | [diff] [blame] | 62 | and provide secure encrypted communications between two untrusted hosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 63 | over an insecure network. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 64 | .Pp |
| 65 | .Nm |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 66 | listens for connections from clients. |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 67 | It is normally started at boot from |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 68 | .Pa /etc/rc . |
| 69 | It forks a new |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 70 | daemon for each incoming connection. |
| 71 | The forked daemons handle |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 72 | key exchange, encryption, authentication, command execution, |
| 73 | and data exchange. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 74 | .Pp |
| 75 | .Nm |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 76 | can be configured using command-line options or a configuration file |
| 77 | (by default |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 78 | .Xr sshd_config 5 ) ; |
| 79 | command-line options override values specified in the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 80 | configuration file. |
Damien Miller | 6162d12 | 1999-11-21 13:23:52 +1100 | [diff] [blame] | 81 | .Nm |
| 82 | rereads its configuration file when it receives a hangup signal, |
Ben Lindstrom | 49a098d | 2001-03-05 06:55:18 +0000 | [diff] [blame] | 83 | .Dv SIGHUP , |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 84 | by executing itself with the name and options it was started with, e.g.\& |
Ben Lindstrom | 49a098d | 2001-03-05 06:55:18 +0000 | [diff] [blame] | 85 | .Pa /usr/sbin/sshd . |
Damien Miller | 6162d12 | 1999-11-21 13:23:52 +1100 | [diff] [blame] | 86 | .Pp |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 87 | The options are as follows: |
| 88 | .Bl -tag -width Ds |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 89 | .It Fl 4 |
| 90 | Forces |
| 91 | .Nm |
| 92 | to use IPv4 addresses only. |
| 93 | .It Fl 6 |
| 94 | Forces |
| 95 | .Nm |
| 96 | to use IPv6 addresses only. |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 97 | .It Fl C Ar connection_spec |
| 98 | Specify the connection parameters to use for the |
| 99 | .Fl T |
| 100 | extended test mode. |
| 101 | If provided, any |
| 102 | .Cm Match |
dtucker@openbsd.org@openbsd.org | 0208a48 | 2017-11-03 03:18:53 +0000 | [diff] [blame] | 103 | directives in the configuration file that would apply are applied before the |
| 104 | configuration is written to standard output. |
| 105 | The connection parameters are supplied as keyword=value pairs and may be |
| 106 | supplied in any order, either with multiple |
| 107 | .Fl C |
| 108 | options or as a comma-separated list. |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 109 | The keywords are |
dtucker@openbsd.org@openbsd.org | 0208a48 | 2017-11-03 03:18:53 +0000 | [diff] [blame] | 110 | .Dq addr, |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 111 | .Dq user , |
| 112 | .Dq host , |
Darren Tucker | fbcf827 | 2012-05-19 19:37:01 +1000 | [diff] [blame] | 113 | .Dq laddr , |
| 114 | .Dq lport , |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 115 | and |
dtucker@openbsd.org@openbsd.org | 0208a48 | 2017-11-03 03:18:53 +0000 | [diff] [blame] | 116 | .Dq rdomain |
| 117 | and correspond to source address, user, resolved source host name, |
| 118 | local address, local port number and routing domain respectively. |
Damien Miller | 15f5b56 | 2010-03-03 10:25:21 +1100 | [diff] [blame] | 119 | .It Fl c Ar host_certificate_file |
| 120 | Specifies a path to a certificate file to identify |
| 121 | .Nm |
| 122 | during key exchange. |
| 123 | The certificate file must match a host key file specified using the |
| 124 | .Fl h |
| 125 | option or the |
| 126 | .Cm HostKey |
| 127 | configuration directive. |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 128 | .It Fl D |
| 129 | When this option is specified, |
| 130 | .Nm |
| 131 | will not detach and does not become a daemon. |
| 132 | This allows easy monitoring of |
| 133 | .Nm sshd . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 134 | .It Fl d |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 135 | Debug mode. |
Damien Miller | 74d9825 | 2010-02-02 17:01:46 +1100 | [diff] [blame] | 136 | The server sends verbose debug output to standard error, |
| 137 | and does not put itself in the background. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 138 | The server also will not fork and will only process one connection. |
| 139 | This option is only intended for debugging for the server. |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 140 | Multiple |
| 141 | .Fl d |
| 142 | options increase the debugging level. |
Damien Miller | 874d77b | 2000-10-14 16:23:11 +1100 | [diff] [blame] | 143 | Maximum is 3. |
Damien Miller | 03d4d7e | 2013-04-23 15:21:06 +1000 | [diff] [blame] | 144 | .It Fl E Ar log_file |
| 145 | Append debug logs to |
| 146 | .Ar log_file |
| 147 | instead of the system log. |
Ben Lindstrom | c65e6a0 | 2001-04-23 13:02:16 +0000 | [diff] [blame] | 148 | .It Fl e |
Damien Miller | 6901032 | 2013-04-23 15:21:24 +1000 | [diff] [blame] | 149 | Write debug logs to standard error instead of the system log. |
Darren Tucker | 04354b9 | 2007-03-21 20:46:54 +1100 | [diff] [blame] | 150 | .It Fl f Ar config_file |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 151 | Specifies the name of the configuration file. |
| 152 | The default is |
Damien Miller | 05eda43 | 2002-02-10 18:32:28 +1100 | [diff] [blame] | 153 | .Pa /etc/ssh/sshd_config . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 154 | .Nm |
| 155 | refuses to start if there is no configuration file. |
| 156 | .It Fl g Ar login_grace_time |
| 157 | Gives the grace time for clients to authenticate themselves (default |
Damien Miller | c134863 | 2002-09-05 14:35:14 +1000 | [diff] [blame] | 158 | 120 seconds). |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 159 | If the client fails to authenticate the user within |
| 160 | this many seconds, the server disconnects and exits. |
| 161 | A value of zero indicates no limit. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 162 | .It Fl h Ar host_key_file |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 163 | Specifies a file from which a host key is read. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 164 | This option must be given if |
| 165 | .Nm |
| 166 | is not run as root (as the normal |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 167 | host key files are normally not readable by anyone but root). |
| 168 | The default is |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 169 | .Pa /etc/ssh/ssh_host_ecdsa_key , |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 170 | .Pa /etc/ssh/ssh_host_ed25519_key |
Damien Miller | 7fc2373 | 2002-01-22 23:19:11 +1100 | [diff] [blame] | 171 | and |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 172 | .Pa /etc/ssh/ssh_host_rsa_key . |
Ben Lindstrom | 4dccfa5 | 2000-12-28 16:40:05 +0000 | [diff] [blame] | 173 | It is possible to have multiple host key files for |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 174 | the different host key algorithms. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 175 | .It Fl i |
| 176 | Specifies that |
| 177 | .Nm |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 178 | is being run from |
| 179 | .Xr inetd 8 . |
Ben Lindstrom | ade03f6 | 2001-12-06 18:22:17 +0000 | [diff] [blame] | 180 | .It Fl o Ar option |
| 181 | Can be used to give options in the format used in the configuration file. |
| 182 | This is useful for specifying options for which there is no separate |
| 183 | command-line flag. |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 184 | For full details of the options, and their values, see |
| 185 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 186 | .It Fl p Ar port |
| 187 | Specifies the port on which the server listens for connections |
| 188 | (default 22). |
Damien Miller | 7d1ded4 | 2002-01-22 23:09:41 +1100 | [diff] [blame] | 189 | Multiple port options are permitted. |
Damien Miller | d7f308f | 2005-12-24 14:55:16 +1100 | [diff] [blame] | 190 | Ports specified in the configuration file with the |
| 191 | .Cm Port |
| 192 | option are ignored when a command-line port is specified. |
| 193 | Ports specified using the |
| 194 | .Cm ListenAddress |
| 195 | option override command-line ports. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 196 | .It Fl q |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 197 | Quiet mode. |
| 198 | Nothing is sent to the system log. |
| 199 | Normally the beginning, |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 200 | authentication, and termination of each connection is logged. |
Darren Tucker | e7140f2 | 2008-06-10 23:01:51 +1000 | [diff] [blame] | 201 | .It Fl T |
| 202 | Extended test mode. |
| 203 | Check the validity of the configuration file, output the effective configuration |
| 204 | to stdout and then exit. |
| 205 | Optionally, |
| 206 | .Cm Match |
| 207 | rules may be applied by specifying the connection parameters using one or more |
| 208 | .Fl C |
| 209 | options. |
Darren Tucker | e7f3f75 | 2008-06-10 23:06:01 +1000 | [diff] [blame] | 210 | .It Fl t |
| 211 | Test mode. |
| 212 | Only check the validity of the configuration file and sanity of the keys. |
| 213 | This is useful for updating |
| 214 | .Nm |
| 215 | reliably as configuration options may change. |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 216 | .It Fl u Ar len |
| 217 | This option is used to specify the size of the field |
| 218 | in the |
| 219 | .Li utmp |
| 220 | structure that holds the remote host name. |
| 221 | If the resolved host name is longer than |
| 222 | .Ar len , |
| 223 | the dotted decimal value will be used instead. |
| 224 | This allows hosts with very long host names that |
| 225 | overflow this field to still be uniquely identified. |
| 226 | Specifying |
| 227 | .Fl u0 |
| 228 | indicates that only dotted decimal addresses |
| 229 | should be put into the |
| 230 | .Pa utmp |
| 231 | file. |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 232 | .Fl u0 |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 233 | may also be used to prevent |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 234 | .Nm |
| 235 | from making DNS requests unless the authentication |
| 236 | mechanism or configuration requires it. |
| 237 | Authentication mechanisms that may require DNS include |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 238 | .Cm HostbasedAuthentication |
Ben Lindstrom | 6f672c0 | 2001-09-12 17:51:55 +0000 | [diff] [blame] | 239 | and using a |
| 240 | .Cm from="pattern-list" |
| 241 | option in a key file. |
Ben Lindstrom | ea03db9 | 2002-03-05 01:38:57 +0000 | [diff] [blame] | 242 | Configuration options that require DNS include using a |
| 243 | USER@HOST pattern in |
| 244 | .Cm AllowUsers |
| 245 | or |
| 246 | .Cm DenyUsers . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 247 | .El |
Damien Miller | 8bbdf90 | 2006-02-01 22:05:25 +1100 | [diff] [blame] | 248 | .Sh AUTHENTICATION |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 249 | The OpenSSH SSH daemon supports SSH protocol 2 only. |
jmc@openbsd.org | a685ae8 | 2016-02-17 07:38:19 +0000 | [diff] [blame] | 250 | Each host has a host-specific key, |
| 251 | used to identify the host. |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 252 | Whenever a client connects, the daemon responds with its public |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 253 | host key. |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 254 | The client compares the |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 255 | host key against its own database to verify that it has not changed. |
| 256 | Forward security is provided through a Diffie-Hellman key agreement. |
Damien Miller | 8bbdf90 | 2006-02-01 22:05:25 +1100 | [diff] [blame] | 257 | This key agreement results in a shared session key. |
| 258 | The rest of the session is encrypted using a symmetric cipher, currently |
| 259 | 128-bit AES, Blowfish, 3DES, CAST128, Arcfour, 192-bit AES, or 256-bit AES. |
| 260 | The client selects the encryption algorithm |
| 261 | to use from those offered by the server. |
| 262 | Additionally, session integrity is provided |
| 263 | through a cryptographic message authentication code |
djm@openbsd.org | acaf34f | 2017-05-07 23:12:57 +0000 | [diff] [blame] | 264 | (hmac-md5, hmac-sha1, umac-64, umac-128, |
Damien Miller | 20bd453 | 2011-08-06 06:17:30 +1000 | [diff] [blame] | 265 | hmac-sha2-256 or hmac-sha2-512). |
Damien Miller | 8bbdf90 | 2006-02-01 22:05:25 +1100 | [diff] [blame] | 266 | .Pp |
| 267 | Finally, the server and the client enter an authentication dialog. |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 268 | The client tries to authenticate itself using |
Damien Miller | 8bbdf90 | 2006-02-01 22:05:25 +1100 | [diff] [blame] | 269 | host-based authentication, |
| 270 | public key authentication, |
| 271 | challenge-response authentication, |
| 272 | or password authentication. |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 273 | .Pp |
| 274 | Regardless of the authentication type, the account is checked to |
| 275 | ensure that it is accessible. An account is not accessible if it is |
| 276 | locked, listed in |
| 277 | .Cm DenyUsers |
| 278 | or its group is listed in |
| 279 | .Cm DenyGroups |
Damien Miller | 10479cc | 2018-04-10 10:19:02 +1000 | [diff] [blame] | 280 | \&. The definition of a locked account is system dependent. Some platforms |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 281 | have their own account database (eg AIX) and some modify the passwd field ( |
| 282 | .Ql \&*LK\&* |
| 283 | on Solaris and UnixWare, |
| 284 | .Ql \&* |
| 285 | on HP-UX, containing |
| 286 | .Ql Nologin |
| 287 | on Tru64, |
| 288 | a leading |
| 289 | .Ql \&*LOCKED\&* |
| 290 | on FreeBSD and a leading |
Darren Tucker | 1a9176b | 2007-08-17 09:42:32 +1000 | [diff] [blame] | 291 | .Ql \&! |
| 292 | on most Linuxes). |
| 293 | If there is a requirement to disable password authentication |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 294 | for the account while allowing still public-key, then the passwd field |
| 295 | should be set to something other than these values (eg |
| 296 | .Ql NP |
| 297 | or |
| 298 | .Ql \&*NP\&* |
| 299 | ). |
| 300 | .Pp |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 301 | If the client successfully authenticates itself, a dialog for |
| 302 | preparing the session is entered. |
| 303 | At this time the client may request |
| 304 | things like allocating a pseudo-tty, forwarding X11 connections, |
| 305 | forwarding TCP connections, or forwarding the authentication agent |
| 306 | connection over the secure channel. |
| 307 | .Pp |
Damien Miller | c47d7e9 | 2006-03-15 11:27:20 +1100 | [diff] [blame] | 308 | After this, the client either requests a shell or execution of a command. |
Damien Miller | 99cc4a8 | 2006-01-31 21:45:53 +1100 | [diff] [blame] | 309 | The sides then enter session mode. |
| 310 | In this mode, either side may send |
| 311 | data at any time, and such data is forwarded to/from the shell or |
| 312 | command on the server side, and the user terminal in the client side. |
| 313 | .Pp |
| 314 | When the user program terminates and all forwarded X11 and other |
| 315 | connections have been closed, the server sends command exit status to |
| 316 | the client, and both sides exit. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 317 | .Sh LOGIN PROCESS |
| 318 | When a user successfully logs in, |
| 319 | .Nm |
| 320 | does the following: |
| 321 | .Bl -enum -offset indent |
| 322 | .It |
| 323 | If the login is on a tty, and no command has been specified, |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 324 | prints last login time and |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 325 | .Pa /etc/motd |
| 326 | (unless prevented in the configuration file or by |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 327 | .Pa ~/.hushlogin ; |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 328 | see the |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 329 | .Sx FILES |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 330 | section). |
| 331 | .It |
| 332 | If the login is on a tty, records login time. |
| 333 | .It |
| 334 | Checks |
| 335 | .Pa /etc/nologin ; |
| 336 | if it exists, prints contents and quits |
| 337 | (unless root). |
| 338 | .It |
| 339 | Changes to run with normal user privileges. |
| 340 | .It |
| 341 | Sets up basic environment. |
| 342 | .It |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 343 | Reads the file |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 344 | .Pa ~/.ssh/environment , |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 345 | if it exists, and users are allowed to change their environment. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 346 | See the |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 347 | .Cm PermitUserEnvironment |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 348 | option in |
Ben Lindstrom | dc7adf2 | 2002-08-20 18:38:02 +0000 | [diff] [blame] | 349 | .Xr sshd_config 5 . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 350 | .It |
| 351 | Changes to user's home directory. |
| 352 | .It |
| 353 | If |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 354 | .Pa ~/.ssh/rc |
Damien Miller | 72e6b5c | 2014-07-04 09:00:04 +1000 | [diff] [blame] | 355 | exists and the |
| 356 | .Xr sshd_config 5 |
| 357 | .Cm PermitUserRC |
| 358 | option is set, runs it; else if |
Damien Miller | afcc225 | 2002-02-10 18:32:55 +1100 | [diff] [blame] | 359 | .Pa /etc/ssh/sshrc |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 360 | exists, runs |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 361 | it; otherwise runs xauth. |
| 362 | The |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 363 | .Dq rc |
| 364 | files are given the X11 |
| 365 | authentication protocol and cookie in standard input. |
Damien Miller | fd725cf | 2006-03-15 11:35:54 +1100 | [diff] [blame] | 366 | See |
| 367 | .Sx SSHRC , |
| 368 | below. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 369 | .It |
| 370 | Runs user's shell or command. |
djm@openbsd.org | 8d4d1bf | 2015-05-01 07:11:47 +0000 | [diff] [blame] | 371 | All commands are run under the user's login shell as specified in the |
| 372 | system password database. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 373 | .El |
Damien Miller | fd725cf | 2006-03-15 11:35:54 +1100 | [diff] [blame] | 374 | .Sh SSHRC |
| 375 | If the file |
| 376 | .Pa ~/.ssh/rc |
| 377 | exists, |
| 378 | .Xr sh 1 |
| 379 | runs it after reading the |
| 380 | environment files but before starting the user's shell or command. |
| 381 | It must not produce any output on stdout; stderr must be used |
| 382 | instead. |
| 383 | If X11 forwarding is in use, it will receive the "proto cookie" pair in |
| 384 | its standard input (and |
| 385 | .Ev DISPLAY |
| 386 | in its environment). |
| 387 | The script must call |
| 388 | .Xr xauth 1 |
| 389 | because |
| 390 | .Nm |
| 391 | will not run xauth automatically to add X11 cookies. |
| 392 | .Pp |
| 393 | The primary purpose of this file is to run any initialization routines |
| 394 | which may be needed before the user's home directory becomes |
| 395 | accessible; AFS is a particular example of such an environment. |
| 396 | .Pp |
| 397 | This file will probably contain some initialization code followed by |
| 398 | something similar to: |
| 399 | .Bd -literal -offset 3n |
| 400 | if read proto cookie && [ -n "$DISPLAY" ]; then |
| 401 | if [ `echo $DISPLAY | cut -c1-10` = 'localhost:' ]; then |
| 402 | # X11UseLocalhost=yes |
| 403 | echo add unix:`echo $DISPLAY | |
| 404 | cut -c11-` $proto $cookie |
| 405 | else |
| 406 | # X11UseLocalhost=no |
| 407 | echo add $DISPLAY $proto $cookie |
| 408 | fi | xauth -q - |
| 409 | fi |
| 410 | .Ed |
| 411 | .Pp |
| 412 | If this file does not exist, |
| 413 | .Pa /etc/ssh/sshrc |
| 414 | is run, and if that |
| 415 | does not exist either, xauth is used to add the cookie. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 416 | .Sh AUTHORIZED_KEYS FILE FORMAT |
Ben Lindstrom | f96704d | 2001-06-25 04:17:12 +0000 | [diff] [blame] | 417 | .Cm AuthorizedKeysFile |
Damien Miller | b9132fc | 2011-05-29 21:41:40 +1000 | [diff] [blame] | 418 | specifies the files containing public keys for |
Damien Miller | dcfea27 | 2006-03-15 11:31:22 +1100 | [diff] [blame] | 419 | public key authentication; |
djm@openbsd.org | 2bca8a4 | 2015-09-11 03:13:36 +0000 | [diff] [blame] | 420 | if this option is not specified, the default is |
Damien Miller | d8478b6 | 2011-05-29 21:39:36 +1000 | [diff] [blame] | 421 | .Pa ~/.ssh/authorized_keys |
| 422 | and |
| 423 | .Pa ~/.ssh/authorized_keys2 . |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 424 | Each line of the file contains one |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 425 | key (empty lines and lines starting with a |
| 426 | .Ql # |
| 427 | are ignored as |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 428 | comments). |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 429 | Public keys consist of the following space-separated fields: |
Damien Miller | dcfea27 | 2006-03-15 11:31:22 +1100 | [diff] [blame] | 430 | options, keytype, base64-encoded key, comment. |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 431 | The options field is optional. |
naddy@openbsd.org | aa4c640 | 2019-11-07 08:38:38 +0000 | [diff] [blame] | 432 | The supported key types are: |
| 433 | .Pp |
| 434 | .Bl -item -compact -offset indent |
| 435 | .It |
| 436 | sk-ecdsa-sha2-nistp256@openssh.com |
| 437 | .It |
| 438 | ecdsa-sha2-nistp256 |
| 439 | .It |
| 440 | ecdsa-sha2-nistp384 |
| 441 | .It |
| 442 | ecdsa-sha2-nistp521 |
| 443 | .It |
djm@openbsd.org | e2e1283 | 2019-11-18 04:55:02 +0000 | [diff] [blame] | 444 | sk-ssh-ed25519@openssh.com |
| 445 | .It |
naddy@openbsd.org | aa4c640 | 2019-11-07 08:38:38 +0000 | [diff] [blame] | 446 | ssh-ed25519 |
| 447 | .It |
| 448 | ssh-dss |
| 449 | .It |
| 450 | ssh-rsa |
| 451 | .El |
| 452 | .Pp |
| 453 | The comment field is not used for anything (but may be convenient for the |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 454 | user to identify the key). |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 455 | .Pp |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 456 | Note that lines in this file can be several hundred bytes long |
Darren Tucker | 22cc741 | 2004-12-06 22:47:41 +1100 | [diff] [blame] | 457 | (because of the size of the public key encoding) up to a limit of |
naddy@openbsd.org | aa4c640 | 2019-11-07 08:38:38 +0000 | [diff] [blame] | 458 | 8 kilobytes, which permits RSA keys up to 16 kilobits. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 459 | You don't want to type them in; instead, copy the |
Damien Miller | dcfea27 | 2006-03-15 11:31:22 +1100 | [diff] [blame] | 460 | .Pa id_dsa.pub , |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 461 | .Pa id_ecdsa.pub , |
naddy@openbsd.org | aa4c640 | 2019-11-07 08:38:38 +0000 | [diff] [blame] | 462 | .Pa id_ecdsa_sk.pub , |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 463 | .Pa id_ed25519.pub , |
djm@openbsd.org | e2e1283 | 2019-11-18 04:55:02 +0000 | [diff] [blame] | 464 | .Pa id_ed25519_sk.pub , |
Ben Lindstrom | 18a82ac | 2001-04-11 15:59:35 +0000 | [diff] [blame] | 465 | or the |
| 466 | .Pa id_rsa.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 467 | file and edit it. |
| 468 | .Pp |
Ben Lindstrom | 0d0be02 | 2002-04-02 20:39:29 +0000 | [diff] [blame] | 469 | .Nm |
dtucker@openbsd.org | 055e09e | 2018-03-03 06:37:53 +0000 | [diff] [blame] | 470 | enforces a minimum RSA key modulus size of 1024 bits. |
Ben Lindstrom | 0d0be02 | 2002-04-02 20:39:29 +0000 | [diff] [blame] | 471 | .Pp |
Damien Miller | 942da03 | 2000-08-18 13:59:06 +1000 | [diff] [blame] | 472 | The options (if present) consist of comma-separated option |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 473 | specifications. |
| 474 | No spaces are permitted, except within double quotes. |
Ben Lindstrom | 1c0fd09 | 2001-09-12 16:36:17 +0000 | [diff] [blame] | 475 | The following option specifications are supported (note |
| 476 | that option keywords are case-insensitive): |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 477 | .Bl -tag -width Ds |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 478 | .It Cm agent-forwarding |
| 479 | Enable authentication agent forwarding previously disabled by the |
| 480 | .Cm restrict |
| 481 | option. |
Damien Miller | cd38c9c | 2010-03-04 21:51:37 +1100 | [diff] [blame] | 482 | .It Cm cert-authority |
Damien Miller | 0a80ca1 | 2010-02-27 07:55:05 +1100 | [diff] [blame] | 483 | Specifies that the listed key is a certification authority (CA) that is |
| 484 | trusted to validate signed certificates for user authentication. |
| 485 | .Pp |
| 486 | Certificates may encode access restrictions similar to these key options. |
| 487 | If both certificate restrictions and key options are present, the most |
| 488 | restrictive union of the two is applied. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 489 | .It Cm command="command" |
| 490 | Specifies that the command is executed whenever this key is used for |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 491 | authentication. |
| 492 | The command supplied by the user (if any) is ignored. |
Ben Lindstrom | 23124ea | 2001-09-14 23:14:25 +0000 | [diff] [blame] | 493 | The command is run on a pty if the client requests a pty; |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 494 | otherwise it is run without a tty. |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 495 | If an 8-bit clean channel is required, |
Ben Lindstrom | 594e203 | 2001-09-12 18:35:30 +0000 | [diff] [blame] | 496 | one must not request a pty or should specify |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 497 | .Cm no-pty . |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 498 | A quote may be included in the command by quoting it with a backslash. |
djm@openbsd.org | fd6dcef | 2016-11-30 02:57:40 +0000 | [diff] [blame] | 499 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 500 | This option might be useful |
Damien Miller | b83df8d | 2002-09-04 16:24:55 +1000 | [diff] [blame] | 501 | to restrict certain public keys to perform just a specific operation. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 502 | An example might be a key that permits remote backups but nothing else. |
Damien Miller | 7c24b81 | 2006-01-14 10:09:56 +1100 | [diff] [blame] | 503 | Note that the client may specify TCP and/or X11 |
djm@openbsd.org | fd6dcef | 2016-11-30 02:57:40 +0000 | [diff] [blame] | 504 | forwarding unless they are explicitly prohibited, e.g. using the |
| 505 | .Cm restrict |
| 506 | key option. |
| 507 | .Pp |
Damien Miller | e275443 | 2006-07-24 14:06:47 +1000 | [diff] [blame] | 508 | The command originally supplied by the client is available in the |
| 509 | .Ev SSH_ORIGINAL_COMMAND |
| 510 | environment variable. |
Ben Lindstrom | 20daef7 | 2001-09-20 00:54:01 +0000 | [diff] [blame] | 511 | Note that this option applies to shell, command or subsystem execution. |
djm@openbsd.org | fd6dcef | 2016-11-30 02:57:40 +0000 | [diff] [blame] | 512 | Also note that this command may be superseded by a |
Damien Miller | 0a80ca1 | 2010-02-27 07:55:05 +1100 | [diff] [blame] | 513 | .Xr sshd_config 5 |
| 514 | .Cm ForceCommand |
djm@openbsd.org | fd6dcef | 2016-11-30 02:57:40 +0000 | [diff] [blame] | 515 | directive. |
| 516 | .Pp |
| 517 | If a command is specified and a forced-command is embedded in a certificate |
| 518 | used for authentication, then the certificate will be accepted only if the |
| 519 | two commands are identical. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 520 | .It Cm environment="NAME=value" |
| 521 | Specifies that the string is to be added to the environment when |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 522 | logging in using this key. |
| 523 | Environment variables set this way |
| 524 | override other default environment values. |
| 525 | Multiple options of this type are permitted. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 526 | Environment processing is disabled by default and is |
| 527 | controlled via the |
| 528 | .Cm PermitUserEnvironment |
| 529 | option. |
jmc@openbsd.org | 037fdc1 | 2018-03-14 06:56:20 +0000 | [diff] [blame] | 530 | .It Cm expiry-time="timespec" |
| 531 | Specifies a time after which the key will not be accepted. |
| 532 | The time may be specified as a YYYYMMDD date or a YYYYMMDDHHMM[SS] time |
| 533 | in the system time-zone. |
Damien Miller | 31bdc52 | 2006-03-15 11:31:44 +1100 | [diff] [blame] | 534 | .It Cm from="pattern-list" |
Darren Tucker | 896ad5a | 2008-06-11 09:34:46 +1000 | [diff] [blame] | 535 | Specifies that in addition to public key authentication, either the canonical |
Darren Tucker | 1199673 | 2008-06-13 04:32:00 +1000 | [diff] [blame] | 536 | name of the remote host or its IP address must be present in the |
Darren Tucker | 896ad5a | 2008-06-11 09:34:46 +1000 | [diff] [blame] | 537 | comma-separated list of patterns. |
Damien Miller | fecfd11 | 2013-07-18 16:11:50 +1000 | [diff] [blame] | 538 | See PATTERNS in |
Damien Miller | c7d5b5e | 2006-03-15 11:55:08 +1100 | [diff] [blame] | 539 | .Xr ssh_config 5 |
| 540 | for more information on patterns. |
Darren Tucker | 896ad5a | 2008-06-11 09:34:46 +1000 | [diff] [blame] | 541 | .Pp |
| 542 | In addition to the wildcard matching that may be applied to hostnames or |
| 543 | addresses, a |
| 544 | .Cm from |
Darren Tucker | 5837b51 | 2009-06-21 17:52:27 +1000 | [diff] [blame] | 545 | stanza may match IP addresses using CIDR address/masklen notation. |
Darren Tucker | 896ad5a | 2008-06-11 09:34:46 +1000 | [diff] [blame] | 546 | .Pp |
| 547 | The purpose of this option is to optionally increase security: public key |
| 548 | authentication by itself does not trust the network or name servers or |
| 549 | anything (but the key); however, if somebody somehow steals the key, the key |
| 550 | permits an intruder to log in from anywhere in the world. |
| 551 | This additional option makes using a stolen key more difficult (name |
| 552 | servers and/or routers would have to be compromised in addition to |
| 553 | just the key). |
Damien Miller | 31bdc52 | 2006-03-15 11:31:44 +1100 | [diff] [blame] | 554 | .It Cm no-agent-forwarding |
| 555 | Forbids authentication agent forwarding when this key is used for |
| 556 | authentication. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 557 | .It Cm no-port-forwarding |
Damien Miller | 7c24b81 | 2006-01-14 10:09:56 +1100 | [diff] [blame] | 558 | Forbids TCP forwarding when this key is used for authentication. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 559 | Any port forward requests by the client will return an error. |
Damien Miller | 208f1ed | 2006-03-15 11:56:03 +1100 | [diff] [blame] | 560 | This might be used, e.g. in connection with the |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 561 | .Cm command |
| 562 | option. |
Damien Miller | 31bdc52 | 2006-03-15 11:31:44 +1100 | [diff] [blame] | 563 | .It Cm no-pty |
| 564 | Prevents tty allocation (a request to allocate a pty will fail). |
Damien Miller | 95e8095 | 2008-03-27 11:03:05 +1100 | [diff] [blame] | 565 | .It Cm no-user-rc |
Damien Miller | 13ba9c2 | 2008-04-03 20:52:51 +1100 | [diff] [blame] | 566 | Disables execution of |
Damien Miller | 95e8095 | 2008-03-27 11:03:05 +1100 | [diff] [blame] | 567 | .Pa ~/.ssh/rc . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 568 | .It Cm no-X11-forwarding |
| 569 | Forbids X11 forwarding when this key is used for authentication. |
| 570 | Any X11 forward requests by the client will return an error. |
djm@openbsd.org | 87ddd67 | 2018-06-19 02:59:41 +0000 | [diff] [blame] | 571 | .It Cm permitlisten="[host:]port" |
jmc@openbsd.org | 6ff6fda | 2018-06-07 11:26:14 +0000 | [diff] [blame] | 572 | Limit remote port forwarding with the |
djm@openbsd.org | 803d896 | 2018-06-06 18:24:15 +0000 | [diff] [blame] | 573 | .Xr ssh 1 |
| 574 | .Fl R |
djm@openbsd.org | 87ddd67 | 2018-06-19 02:59:41 +0000 | [diff] [blame] | 575 | option such that it may only listen on the specified host (optional) and port. |
djm@openbsd.org | 803d896 | 2018-06-06 18:24:15 +0000 | [diff] [blame] | 576 | IPv6 addresses can be specified by enclosing the address in square brackets. |
| 577 | Multiple |
| 578 | .Cm permitlisten |
| 579 | options may be applied separated by commas. |
| 580 | Hostnames may include wildcards as described in the PATTERNS section in |
| 581 | .Xr ssh_config 5 . |
| 582 | A port specification of |
| 583 | .Cm * |
| 584 | matches any port. |
| 585 | Note that the setting of |
| 586 | .Cm GatewayPorts |
| 587 | may further restrict listen addresses. |
djm@openbsd.org | 87ddd67 | 2018-06-19 02:59:41 +0000 | [diff] [blame] | 588 | Note that |
| 589 | .Xr ssh 1 |
| 590 | will send a hostname of |
| 591 | .Dq localhost |
| 592 | if a listen host was not specified when the forwarding was requested, and |
jmc@openbsd.org | f535ff9 | 2018-06-19 05:36:57 +0000 | [diff] [blame] | 593 | that this name is treated differently to the explicit localhost addresses |
djm@openbsd.org | 87ddd67 | 2018-06-19 02:59:41 +0000 | [diff] [blame] | 594 | .Dq 127.0.0.1 |
| 595 | and |
| 596 | .Dq ::1 . |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 597 | .It Cm permitopen="host:port" |
jmc@openbsd.org | 6ff6fda | 2018-06-07 11:26:14 +0000 | [diff] [blame] | 598 | Limit local port forwarding with the |
bentley@openbsd.org | da8af83 | 2014-11-15 14:41:03 +0000 | [diff] [blame] | 599 | .Xr ssh 1 |
| 600 | .Fl L |
djm@openbsd.org | 803d896 | 2018-06-06 18:24:15 +0000 | [diff] [blame] | 601 | option such that it may only connect to the specified host and port. |
Damien Miller | 7fa9660 | 2010-08-05 13:03:13 +1000 | [diff] [blame] | 602 | IPv6 addresses can be specified by enclosing the address in square brackets. |
Ben Lindstrom | d71ba57 | 2001-09-12 18:03:31 +0000 | [diff] [blame] | 603 | Multiple |
Damien Miller | a243fde | 2001-03-19 23:16:08 +1100 | [diff] [blame] | 604 | .Cm permitopen |
Damien Miller | fbf486b | 2003-05-23 18:44:23 +1000 | [diff] [blame] | 605 | options may be applied separated by commas. |
| 606 | No pattern matching is performed on the specified hostnames, |
| 607 | they must be literal domains or addresses. |
Darren Tucker | 1338b9e | 2011-10-02 18:57:35 +1100 | [diff] [blame] | 608 | A port specification of |
| 609 | .Cm * |
| 610 | matches any port. |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 611 | .It Cm port-forwarding |
| 612 | Enable port forwarding previously disabled by the |
| 613 | .Cm restrict |
djm@openbsd.org | 2b428f9 | 2018-02-05 04:02:53 +0000 | [diff] [blame] | 614 | option. |
Damien Miller | 30da344 | 2010-05-10 11:58:03 +1000 | [diff] [blame] | 615 | .It Cm principals="principals" |
| 616 | On a |
| 617 | .Cm cert-authority |
| 618 | line, specifies allowed principals for certificate authentication as a |
| 619 | comma-separated list. |
| 620 | At least one name from the list must appear in the certificate's |
| 621 | list of principals for the certificate to be accepted. |
| 622 | This option is ignored for keys that are not marked as trusted certificate |
| 623 | signers using the |
| 624 | .Cm cert-authority |
| 625 | option. |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 626 | .It Cm pty |
| 627 | Permits tty allocation previously disabled by the |
| 628 | .Cm restrict |
| 629 | option. |
djm@openbsd.org | 2e71263 | 2019-11-25 00:54:23 +0000 | [diff] [blame] | 630 | .It Cm no-touch-required |
| 631 | Do not require demonstration of user presence |
| 632 | for signatures made using this key. |
| 633 | This option only makes sense for the Security Key algorithms |
| 634 | .Cm ecdsa-sk |
| 635 | and |
| 636 | .Cm ed25519-sk . |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 637 | .It Cm restrict |
| 638 | Enable all restrictions, i.e. disable port, agent and X11 forwarding, |
| 639 | as well as disabling PTY allocation |
| 640 | and execution of |
| 641 | .Pa ~/.ssh/rc . |
| 642 | If any future restriction capabilities are added to authorized_keys files |
| 643 | they will be included in this set. |
Damien Miller | d27b947 | 2005-12-13 19:29:02 +1100 | [diff] [blame] | 644 | .It Cm tunnel="n" |
| 645 | Force a |
| 646 | .Xr tun 4 |
| 647 | device on the server. |
| 648 | Without this option, the next available device will be used if |
| 649 | the client requests a tunnel. |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 650 | .It Cm user-rc |
| 651 | Enables execution of |
| 652 | .Pa ~/.ssh/rc |
| 653 | previously disabled by the |
| 654 | .Cm restrict |
| 655 | option. |
| 656 | .It Cm X11-forwarding |
| 657 | Permits X11 forwarding previously disabled by the |
| 658 | .Cm restrict |
| 659 | option. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 660 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 661 | .Pp |
Damien Miller | 7d2ef02 | 2006-03-15 11:32:06 +1100 | [diff] [blame] | 662 | An example authorized_keys file: |
Damien Miller | c8f61cf | 2006-03-15 11:33:25 +1100 | [diff] [blame] | 663 | .Bd -literal -offset 3n |
Damien Miller | 7d2ef02 | 2006-03-15 11:32:06 +1100 | [diff] [blame] | 664 | # Comments allowed at start of line |
| 665 | ssh-rsa AAAAB3Nza...LiPk== user@example.net |
Damien Miller | c8f61cf | 2006-03-15 11:33:25 +1100 | [diff] [blame] | 666 | from="*.sales.example.net,!pc.sales.example.net" ssh-rsa |
| 667 | AAAAB2...19Q== john@example.net |
dtucker@openbsd.org | 01c98d9 | 2018-07-22 12:16:59 +0000 | [diff] [blame] | 668 | command="dump /home",no-pty,no-port-forwarding ssh-rsa |
Damien Miller | c8f61cf | 2006-03-15 11:33:25 +1100 | [diff] [blame] | 669 | AAAAC3...51R== example.net |
dtucker@openbsd.org | 01c98d9 | 2018-07-22 12:16:59 +0000 | [diff] [blame] | 670 | permitopen="192.0.2.1:80",permitopen="192.0.2.2:25" ssh-rsa |
Damien Miller | c8f61cf | 2006-03-15 11:33:25 +1100 | [diff] [blame] | 671 | AAAAB5...21S== |
dtucker@openbsd.org | 01c98d9 | 2018-07-22 12:16:59 +0000 | [diff] [blame] | 672 | permitlisten="localhost:8080",permitopen="localhost:22000" ssh-rsa |
djm@openbsd.org | 87ddd67 | 2018-06-19 02:59:41 +0000 | [diff] [blame] | 673 | AAAAB5...21S== |
Damien Miller | c8f61cf | 2006-03-15 11:33:25 +1100 | [diff] [blame] | 674 | tunnel="0",command="sh /etc/netstart tun0" ssh-rsa AAAA...== |
| 675 | jane@example.net |
djm@openbsd.org | 383f10f | 2015-11-16 00:30:02 +0000 | [diff] [blame] | 676 | restrict,command="uptime" ssh-rsa AAAA1C8...32Tv== |
| 677 | user@example.net |
| 678 | restrict,pty,command="nethack" ssh-rsa AAAA1f8...IrrC5== |
| 679 | user@example.net |
djm@openbsd.org | 2e71263 | 2019-11-25 00:54:23 +0000 | [diff] [blame] | 680 | no-touch-required sk-ecdsa-sha2-nistp256@openssh.com AAAAInN...Ko== |
| 681 | user@example.net |
Damien Miller | 7d2ef02 | 2006-03-15 11:32:06 +1100 | [diff] [blame] | 682 | .Ed |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 683 | .Sh SSH_KNOWN_HOSTS FILE FORMAT |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 684 | The |
Damien Miller | ffadc58 | 2003-02-24 11:52:26 +1100 | [diff] [blame] | 685 | .Pa /etc/ssh/ssh_known_hosts |
Damien Miller | 22c7726 | 2000-04-13 12:26:34 +1000 | [diff] [blame] | 686 | and |
Damien Miller | 167ea5d | 2005-05-26 12:04:02 +1000 | [diff] [blame] | 687 | .Pa ~/.ssh/known_hosts |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 688 | files contain host public keys for all known hosts. |
| 689 | The global file should |
| 690 | be prepared by the administrator (optional), and the per-user file is |
dtucker@openbsd.org | 6ba9f89 | 2017-01-30 23:27:39 +0000 | [diff] [blame] | 691 | maintained automatically: whenever the user connects to an unknown host, |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 692 | its key is added to the per-user file. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 693 | .Pp |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 694 | Each line in these files contains the following fields: markers (optional), |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 695 | hostnames, keytype, base64-encoded key, comment. |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 696 | The fields are separated by spaces. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 697 | .Pp |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 698 | The marker is optional, but if it is present then it must be one of |
| 699 | .Dq @cert-authority , |
| 700 | to indicate that the line contains a certification authority (CA) key, |
| 701 | or |
| 702 | .Dq @revoked , |
| 703 | to indicate that the key contained on the line is revoked and must not ever |
| 704 | be accepted. |
| 705 | Only one marker should be used on a key line. |
| 706 | .Pp |
Damien Miller | 3155432 | 2003-05-14 13:44:58 +1000 | [diff] [blame] | 707 | Hostnames is a comma-separated list of patterns |
Damien Miller | 9a7f201 | 2006-03-15 11:32:42 +1100 | [diff] [blame] | 708 | .Pf ( Ql * |
Damien Miller | fbf486b | 2003-05-23 18:44:23 +1000 | [diff] [blame] | 709 | and |
| 710 | .Ql \&? |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 711 | act as |
djm@openbsd.org | 6f8ca3b | 2017-06-24 05:35:05 +0000 | [diff] [blame] | 712 | wildcards); each pattern in turn is matched against the host name. |
| 713 | When |
| 714 | .Nm sshd |
| 715 | is authenticating a client, such as when using |
| 716 | .Cm HostbasedAuthentication , |
| 717 | this will be the canonical client host name. |
| 718 | When |
| 719 | .Xr ssh 1 |
jmc@openbsd.org | e2004d4 | 2017-06-24 06:28:50 +0000 | [diff] [blame] | 720 | is authenticating a server, this will be the host name |
djm@openbsd.org | 6f8ca3b | 2017-06-24 05:35:05 +0000 | [diff] [blame] | 721 | given by the user, the value of the |
| 722 | .Xr ssh 1 |
| 723 | .Cm HostkeyAlias |
| 724 | if it was specified, or the canonical server hostname if the |
| 725 | .Xr ssh 1 |
| 726 | .Cm CanonicalizeHostname |
| 727 | option was used. |
| 728 | .Pp |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 729 | A pattern may also be preceded by |
Damien Miller | 049245d | 2003-05-14 13:44:42 +1000 | [diff] [blame] | 730 | .Ql \&! |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 731 | to indicate negation: if the host name matches a negated |
| 732 | pattern, it is not accepted (by that line) even if it matched another |
| 733 | pattern on the line. |
Darren Tucker | da34553 | 2006-07-10 23:04:19 +1000 | [diff] [blame] | 734 | A hostname or address may optionally be enclosed within |
| 735 | .Ql \&[ |
| 736 | and |
| 737 | .Ql \&] |
| 738 | brackets then followed by |
| 739 | .Ql \&: |
Darren Tucker | 1131847 | 2006-07-12 22:07:59 +1000 | [diff] [blame] | 740 | and a non-standard port number. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 741 | .Pp |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 742 | Alternately, hostnames may be stored in a hashed form which hides host names |
Damien Miller | 718fd4b | 2005-03-02 12:03:23 +1100 | [diff] [blame] | 743 | and addresses should the file's contents be disclosed. |
| 744 | Hashed hostnames start with a |
| 745 | .Ql | |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 746 | character. |
| 747 | Only one hashed hostname may appear on a single line and none of the above |
| 748 | negation or wildcard operators may be applied. |
| 749 | .Pp |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 750 | The keytype and base64-encoded key are taken directly from the host key; they |
Damien Miller | 9a7f201 | 2006-03-15 11:32:42 +1100 | [diff] [blame] | 751 | can be obtained, for example, from |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 752 | .Pa /etc/ssh/ssh_host_rsa_key.pub . |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 753 | The optional comment field continues to the end of the line, and is not used. |
| 754 | .Pp |
| 755 | Lines starting with |
| 756 | .Ql # |
| 757 | and empty lines are ignored as comments. |
| 758 | .Pp |
| 759 | When performing host authentication, authentication is accepted if any |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 760 | matching line has the proper key; either one that matches exactly or, |
| 761 | if the server has presented a certificate for authentication, the key |
| 762 | of the certification authority that signed the certificate. |
| 763 | For a key to be trusted as a certification authority, it must use the |
| 764 | .Dq @cert-authority |
| 765 | marker described above. |
| 766 | .Pp |
| 767 | The known hosts file also provides a facility to mark keys as revoked, |
| 768 | for example when it is known that the associated private key has been |
| 769 | stolen. |
| 770 | Revoked keys are specified by including the |
| 771 | .Dq @revoked |
| 772 | marker at the beginning of the key line, and are never accepted for |
| 773 | authentication or as certification authorities, but instead will |
| 774 | produce a warning from |
| 775 | .Xr ssh 1 |
| 776 | when they are encountered. |
| 777 | .Pp |
| 778 | It is permissible (but not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 779 | recommended) to have several lines or different host keys for the same |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 780 | names. |
| 781 | This will inevitably happen when short forms of host names |
| 782 | from different domains are put in the file. |
| 783 | It is possible |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 784 | that the files contain conflicting information; authentication is |
| 785 | accepted if valid information can be found from either file. |
| 786 | .Pp |
| 787 | Note that the lines in these files are typically hundreds of characters |
| 788 | long, and you definitely don't want to type in the host keys by hand. |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 789 | Rather, generate them by a script, |
| 790 | .Xr ssh-keyscan 1 |
naddy@openbsd.org | ffe6549 | 2016-08-15 12:32:04 +0000 | [diff] [blame] | 791 | or by taking, for example, |
| 792 | .Pa /etc/ssh/ssh_host_rsa_key.pub |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 793 | and adding the host names at the front. |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 794 | .Xr ssh-keygen 1 |
Damien Miller | 9833905 | 2010-03-05 21:30:35 +1100 | [diff] [blame] | 795 | also offers some basic automated editing for |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 796 | .Pa ~/.ssh/known_hosts |
| 797 | including removing hosts matching a host name and converting all host |
| 798 | names to their hashed representations. |
Damien Miller | cc00f5e | 2006-03-15 11:33:00 +1100 | [diff] [blame] | 799 | .Pp |
| 800 | An example ssh_known_hosts file: |
| 801 | .Bd -literal -offset 3n |
| 802 | # Comments allowed at start of line |
| 803 | closenet,...,192.0.2.53 1024 37 159...93 closenet.example.net |
| 804 | cvs.example.net,192.0.2.10 ssh-rsa AAAA1234.....= |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 805 | # A hashed hostname |
| 806 | |1|JfKTdBh7rNbXkVAQCRp4OQoPfmI=|USECr3SWf1JUPsms5AqfD5QfxkM= ssh-rsa |
| 807 | AAAA1234.....= |
Damien Miller | a7dab8b | 2010-03-05 10:42:05 +1100 | [diff] [blame] | 808 | # A revoked key |
| 809 | @revoked * ssh-rsa AAAAB5W... |
| 810 | # A CA key, accepted for any host in *.mydomain.com or *.mydomain.org |
| 811 | @cert-authority *.mydomain.org,*.mydomain.com ssh-rsa AAAAB5W... |
Damien Miller | e177615 | 2005-03-01 21:47:37 +1100 | [diff] [blame] | 812 | .Ed |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 813 | .Sh FILES |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 814 | .Bl -tag -width Ds -compact |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 815 | .It Pa ~/.hushlogin |
Damien Miller | 70a908e | 2005-03-01 21:17:09 +1100 | [diff] [blame] | 816 | This file is used to suppress printing the last login time and |
| 817 | .Pa /etc/motd , |
| 818 | if |
| 819 | .Cm PrintLastLog |
| 820 | and |
| 821 | .Cm PrintMotd , |
| 822 | respectively, |
| 823 | are enabled. |
| 824 | It does not suppress printing of the banner specified by |
| 825 | .Cm Banner . |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 826 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 827 | .It Pa ~/.rhosts |
Damien Miller | adc35b9 | 2006-03-15 11:35:27 +1100 | [diff] [blame] | 828 | This file is used for host-based authentication (see |
| 829 | .Xr ssh 1 |
| 830 | for more information). |
| 831 | On some machines this file may need to be |
| 832 | world-readable if the user's home directory is on an NFS partition, |
| 833 | because |
| 834 | .Nm |
| 835 | reads it as root. |
| 836 | Additionally, this file must be owned by the user, |
| 837 | and must not have write permissions for anyone else. |
| 838 | The recommended |
| 839 | permission for most machines is read/write for the user, and not |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 840 | accessible by others. |
| 841 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 842 | .It Pa ~/.shosts |
Damien Miller | adc35b9 | 2006-03-15 11:35:27 +1100 | [diff] [blame] | 843 | This file is used in exactly the same way as |
| 844 | .Pa .rhosts , |
| 845 | but allows host-based authentication without permitting login with |
| 846 | rlogin/rsh. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 847 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 848 | .It Pa ~/.ssh/ |
Damien Miller | 520e615 | 2008-02-10 22:46:22 +1100 | [diff] [blame] | 849 | This directory is the default location for all user-specific configuration |
| 850 | and authentication information. |
| 851 | There is no general requirement to keep the entire contents of this directory |
| 852 | secret, but the recommended permissions are read/write/execute for the user, |
| 853 | and not accessible by others. |
| 854 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 855 | .It Pa ~/.ssh/authorized_keys |
sobrado@openbsd.org | f70b22b | 2014-08-30 15:33:50 +0000 | [diff] [blame] | 856 | Lists the public keys (DSA, ECDSA, Ed25519, RSA) |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 857 | that can be used for logging in as this user. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 858 | The format of this file is described above. |
Damien Miller | 5d43d49 | 2006-08-30 11:07:00 +1000 | [diff] [blame] | 859 | The content of the file is not highly sensitive, but the recommended |
Damien Miller | adc35b9 | 2006-03-15 11:35:27 +1100 | [diff] [blame] | 860 | permissions are read/write for the user, and not accessible by others. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 861 | .Pp |
Damien Miller | 5d43d49 | 2006-08-30 11:07:00 +1000 | [diff] [blame] | 862 | If this file, the |
| 863 | .Pa ~/.ssh |
| 864 | directory, or the user's home directory are writable |
| 865 | by other users, then the file could be modified or replaced by unauthorized |
| 866 | users. |
| 867 | In this case, |
| 868 | .Nm |
| 869 | will not allow it to be used unless the |
| 870 | .Cm StrictModes |
| 871 | option has been set to |
| 872 | .Dq no . |
Damien Miller | 5d43d49 | 2006-08-30 11:07:00 +1000 | [diff] [blame] | 873 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 874 | .It Pa ~/.ssh/environment |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 875 | This file is read into the environment at login (if it exists). |
| 876 | It can only contain empty lines, comment lines (that start with |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 877 | .Ql # ) , |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 878 | and assignment lines of the form name=value. |
| 879 | The file should be writable |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 880 | only by the user; it need not be readable by anyone else. |
Ben Lindstrom | bd9bf38 | 2002-08-20 18:54:20 +0000 | [diff] [blame] | 881 | Environment processing is disabled by default and is |
| 882 | controlled via the |
| 883 | .Cm PermitUserEnvironment |
| 884 | option. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 885 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 886 | .It Pa ~/.ssh/known_hosts |
Damien Miller | adc35b9 | 2006-03-15 11:35:27 +1100 | [diff] [blame] | 887 | Contains a list of host keys for all hosts the user has logged into |
| 888 | that are not already in the systemwide list of known host keys. |
| 889 | The format of this file is described above. |
| 890 | This file should be writable only by root/the owner and |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 891 | can, but need not be, world-readable. |
| 892 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 893 | .It Pa ~/.ssh/rc |
Damien Miller | fd725cf | 2006-03-15 11:35:54 +1100 | [diff] [blame] | 894 | Contains initialization routines to be run before |
| 895 | the user's home directory becomes accessible. |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 896 | This file should be writable only by the user, and need not be |
| 897 | readable by anyone else. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 898 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 899 | .It Pa /etc/hosts.equiv |
Damien Miller | 445121f | 2006-03-15 11:36:18 +1100 | [diff] [blame] | 900 | This file is for host-based authentication (see |
| 901 | .Xr ssh 1 ) . |
| 902 | It should only be writable by root. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 903 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 904 | .It Pa /etc/moduli |
djm@openbsd.org | deae7d5 | 2016-02-05 03:07:06 +0000 | [diff] [blame] | 905 | Contains Diffie-Hellman groups used for the "Diffie-Hellman Group Exchange" |
| 906 | key exchange method. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 907 | The file format is described in |
| 908 | .Xr moduli 5 . |
djm@openbsd.org | deae7d5 | 2016-02-05 03:07:06 +0000 | [diff] [blame] | 909 | If no usable groups are found in this file then fixed internal groups will |
| 910 | be used. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 911 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 912 | .It Pa /etc/motd |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 913 | See |
| 914 | .Xr motd 5 . |
| 915 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 916 | .It Pa /etc/nologin |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 917 | If this file exists, |
| 918 | .Nm |
| 919 | refuses to let anyone except root log in. |
| 920 | The contents of the file |
| 921 | are displayed to anyone trying to log in, and non-root connections are |
| 922 | refused. |
| 923 | The file should be world-readable. |
| 924 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 925 | .It Pa /etc/shosts.equiv |
Damien Miller | 445121f | 2006-03-15 11:36:18 +1100 | [diff] [blame] | 926 | This file is used in exactly the same way as |
| 927 | .Pa hosts.equiv , |
| 928 | but allows host-based authentication without permitting login with |
| 929 | rlogin/rsh. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 930 | .Pp |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 931 | .It Pa /etc/ssh/ssh_host_ecdsa_key |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 932 | .It Pa /etc/ssh/ssh_host_ed25519_key |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 933 | .It Pa /etc/ssh/ssh_host_rsa_key |
Damien Miller | b9902cf | 2012-06-20 21:52:58 +1000 | [diff] [blame] | 934 | These files contain the private parts of the host keys. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 935 | These files should only be owned by root, readable only by root, and not |
| 936 | accessible to others. |
| 937 | Note that |
| 938 | .Nm |
Damien Miller | edd0375 | 2006-03-15 11:36:45 +1100 | [diff] [blame] | 939 | does not start if these files are group/world-accessible. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 940 | .Pp |
Damien Miller | eb8b60e | 2010-08-31 22:41:14 +1000 | [diff] [blame] | 941 | .It Pa /etc/ssh/ssh_host_ecdsa_key.pub |
Damien Miller | 8ba0ead | 2013-12-18 17:46:27 +1100 | [diff] [blame] | 942 | .It Pa /etc/ssh/ssh_host_ed25519_key.pub |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 943 | .It Pa /etc/ssh/ssh_host_rsa_key.pub |
Damien Miller | b9902cf | 2012-06-20 21:52:58 +1000 | [diff] [blame] | 944 | These files contain the public parts of the host keys. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 945 | These files should be world-readable but writable only by |
| 946 | root. |
| 947 | Their contents should match the respective private parts. |
| 948 | These files are not |
| 949 | really used for anything; they are provided for the convenience of |
| 950 | the user so their contents can be copied to known hosts files. |
| 951 | These files are created using |
| 952 | .Xr ssh-keygen 1 . |
| 953 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 954 | .It Pa /etc/ssh/ssh_known_hosts |
Darren Tucker | 04354b9 | 2007-03-21 20:46:54 +1100 | [diff] [blame] | 955 | Systemwide list of known host keys. |
| 956 | This file should be prepared by the |
| 957 | system administrator to contain the public host keys of all machines in the |
| 958 | organization. |
| 959 | The format of this file is described above. |
| 960 | This file should be writable only by root/the owner and |
| 961 | should be world-readable. |
| 962 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 963 | .It Pa /etc/ssh/sshd_config |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 964 | Contains configuration data for |
| 965 | .Nm sshd . |
| 966 | The file format and configuration options are described in |
| 967 | .Xr sshd_config 5 . |
| 968 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 969 | .It Pa /etc/ssh/sshrc |
Damien Miller | fd725cf | 2006-03-15 11:35:54 +1100 | [diff] [blame] | 970 | Similar to |
| 971 | .Pa ~/.ssh/rc , |
| 972 | it can be used to specify |
Damien Miller | 450a7a1 | 2000-03-26 13:04:51 +1000 | [diff] [blame] | 973 | machine-specific login-time initializations globally. |
| 974 | This file should be writable only by root, and should be world-readable. |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 975 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 976 | .It Pa /var/empty |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 977 | .Xr chroot 2 |
| 978 | directory used by |
| 979 | .Nm |
| 980 | during privilege separation in the pre-authentication phase. |
| 981 | The directory should not contain any files and must be owned by root |
| 982 | and not group or world-writable. |
| 983 | .Pp |
Damien Miller | afdae61 | 2010-08-31 22:31:14 +1000 | [diff] [blame] | 984 | .It Pa /var/run/sshd.pid |
Damien Miller | d8702e8 | 2006-03-15 11:33:56 +1100 | [diff] [blame] | 985 | Contains the process ID of the |
| 986 | .Nm |
| 987 | listening for connections (if there are several daemons running |
| 988 | concurrently for different ports, this contains the process ID of the one |
| 989 | started last). |
| 990 | The content of this file is not sensitive; it can be world-readable. |
Damien Miller | 3702396 | 2000-07-11 17:31:38 +1000 | [diff] [blame] | 991 | .El |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 992 | .Sh SEE ALSO |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 993 | .Xr scp 1 , |
Damien Miller | 3380426 | 2001-02-04 23:20:18 +1100 | [diff] [blame] | 994 | .Xr sftp 1 , |
Damien Miller | 32aa144 | 1999-10-29 09:15:49 +1000 | [diff] [blame] | 995 | .Xr ssh 1 , |
| 996 | .Xr ssh-add 1 , |
| 997 | .Xr ssh-agent 1 , |
| 998 | .Xr ssh-keygen 1 , |
Darren Tucker | 04354b9 | 2007-03-21 20:46:54 +1100 | [diff] [blame] | 999 | .Xr ssh-keyscan 1 , |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 1000 | .Xr chroot 2 , |
Ben Lindstrom | c8e29ce | 2001-08-06 20:55:28 +0000 | [diff] [blame] | 1001 | .Xr login.conf 5 , |
| 1002 | .Xr moduli 5 , |
Ben Lindstrom | 9f04903 | 2002-06-21 00:59:05 +0000 | [diff] [blame] | 1003 | .Xr sshd_config 5 , |
Darren Tucker | 1f20394 | 2003-10-15 15:50:42 +1000 | [diff] [blame] | 1004 | .Xr inetd 8 , |
Ben Lindstrom | d2bf0d6 | 2001-06-25 04:10:54 +0000 | [diff] [blame] | 1005 | .Xr sftp-server 8 |
Damien Miller | f1ce505 | 2003-06-11 22:04:39 +1000 | [diff] [blame] | 1006 | .Sh AUTHORS |
| 1007 | OpenSSH is a derivative of the original and free |
| 1008 | ssh 1.2.12 release by Tatu Ylonen. |
| 1009 | Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, |
| 1010 | Theo de Raadt and Dug Song |
| 1011 | removed many bugs, re-added newer features and |
| 1012 | created OpenSSH. |
| 1013 | Markus Friedl contributed the support for SSH |
| 1014 | protocol versions 1.5 and 2.0. |
| 1015 | Niels Provos and Markus Friedl contributed support |
| 1016 | for privilege separation. |